Add-AvailabilityAddressSpace -forestname <ZIMBRA SYSTEMS's FQDN>
>
> -accessmethod publicfolder
>
>
>
> This command references Zimbra’s System FQDN. What would this be
> exactly – the zimbra domain name, the zimbra FQDN as in
> server.domain.com or anything else.
>
> I think when we did this function we used the Exchange Forest name as
> documented in other places. This may be why the Zimbra’s F/B info
> isn’t updating on Exchange.

Can anyone confirm where to get the zimbra system FQDN (simply is it the server.domain.com name?)
May see simple, but I want to confirm 100%.

in our scenario we are using split domain with a single namespace, so the FQDN will be out smtp.com ... any free busy lookup for mailboxes not hosted in exchange will be routed to the CAS and then referenced to the server name specified to lookup zimbra free busy and return the results to Exchange users.